This invention relates to a pleated plastic container which can be folded and stored in a minimum space.
A conventional pleated plastic container has a property of being unfolded or opened due to the resiliecy of each pleat, unless the inner space of the container maintains vaccum. Therefore, when not in use, the pleated container is pushed in the pleated direction for decreasing volume. Thereafter, a mouth of the container is closed by a plug for preventing the incoming of the outside air.
However, because the container itself is made of a plastic material which is expanded and contracted depending on the change of the atmospheric temperature, a perfect sealing between the mouth portion and the plug can not be expected.
As time passes, a folded pleated container is opened or unfolded. This phenomenon shows that the vacuum of the inner space of the container is not perfectly maintained.
It is not desirable that some portion or whole body of the folded container is unfolded.
For example, it is desirable that disposable water containers or various beverage containers should occupy a minimum space when folded and discarded. The minimum volume of such containers should be maintained when used containers are collected, transported and regenerated for cost saving and work convenience. Accordingly, the pleated containers should have minimum volume even after they are discarded.
For preventing the opening or unfolding of folded containers, strings are used to tie the containers or heavy things such as bricks often are placed on the containers. It is cumbersome and ugly to tie the containers with strings or to place bricks on the containers.
For overcoming such disadvantages, Japanese Utility Model Publication No. 44-4947 and Utility Model Open Publication No. 54-64641 disclose a pleated container having a protrusion on the inner periphery of a mouth portion. When folding the pleated container, the protrusion is folded and locked against the bottom of the container body. The prior container tends to be unfolded due to a large restoring force of the material thereof.